Abstract

The Wade n+1 rule$^{[1]}$ and the mno rule$^{[2]}$ describe the electronic requirements for the stability of polyhedral boranes (e.g., 1) and macropolyhedral boranes (e.g., 2 and 3), respectively (see Figure 1). Though useful in explaining and designing structures, electron-counting rules provide a yes or no answer; not all molecules having the stipulated numbers of electrons are equally stable. It is desirable to have a qualitative understanding, wherever possible, of the factors that control the relative stability of a family of molecules. We formulated the concept of compatibility of orbitals to explain the relative stability of polyhedral boranes, carboranes, and metallaboranes.$^{[3]}$ Herein we demonstrate that similar concepts can be used to determine the best combination of polyhedra for the formation of condensed macropolyhedral boranes.